Witch-wannabe high school student, who was bullied in school, tried to call on a demon to hurt the bullies and accidentally opens the Hellmouth. Or I would simply be meditating, repeating a Godesses name as a mantra, whoc would be called forth, pick up on my pain, and start killing of the bullies. I might not even know what I was doing at first. Then Buffy and the others would find out, tell me and ask me to stop. But I would be desperate to keep the power, being in denial and not realizing I had no control at all, and almost killing buffy and myself in the process.
I have a feeling I'd do something dumb like that.